Chipless production of tapered gears having spirally arranged teeth

ABSTRACT

The chipless production of tapered or bevel gears having spirally arranged teeth, by either forging or rolling, where a die member and a prospective gear are relatively approached in the direction of the axis of one of said members. There is a relative approach in the direction of the axis of the tapered gear accompanied by a relative turning motion between the gear and the die member and about said axis. The relative approach is essentially a helical motion of the same hand as the hand of the spirally arranged teeth.

United States Patent Inventor Ernest Wildhaber Rochester, N.Y.

Appl. No. 784,350

Filed Dec. 17, 1968 Patented June 8, 1971 Assignee The Gleason WorksRochester, N.Y.

CHIPLESS PRODUCTION OF TAPERED GEARS HAVING SPIRALLY ARRANGED TEETH 8Claims, 11 Drawing Figs.

U.S. Cl 72/84, 72/102, 29/1592 Int. Cl B2lh 5/04, B21k 1/30 Field ofSearch 72/80, 82, 84, 86, 87, 94, 406, 418; 29/1592; 72/102 ReferencesCited UNITED STATES PATENTS 1,240,914 9/19 I 7 Anderson 72/84 1,850,3953/1932 Hughes 29/159.01 2,883,894 4/1959 Tsuchikawa 72/105 FOREIGNPATENTS 885,103 12/1961 Great Britain 29/1592 Primary Examiner Lowell A.Larson Attorneys-Cushman, Darby & Cushman and Morton A.

Polster ABSTRACT: The chipless production of tapered or bevel gearshaving spirally arranged teeth, by either forging or rolling, where adie member and a prospective gear are relatively approached in thedirection of the axis of one of said members. There is a relativeapproach in the direction of the axis of the tapered gear accompanied bya relative turning motion between the gear and the die member and aboutsaid axis. The relative approach is essentially a helical motion of thesame hand as the hand of the spirally arranged teeth.

PATENTED JUN s :97:

SHEET 1 BF 2 FIG.2

FIG.5

I FIG? INVENTOR.

- ERNEST WILDHABER ATTORNEY PATENIED Jun 8137! SHEEI 2 OF 2 INVENTOR.

ERNEST WILDHABER CI-IIFLESE PRODUCTION OF TAIERED GEARS HAVING SPIRALLYARRANGED TEETH The present invention relates to the production oftapered or bevel gears, and in particular to the production by eitherforging or rolling techniques, of such gears having spirally arrangedteeth.

Tapered gears with spirally arranged teeth have oppositely facing toothsurfaces unequally inclined to an axial viewing direction. Likewise theopposite tooth profiles of any cylindrical section coaxial with the gearare unequally inclined to the direction of the gear axis. An approachbetween the die member and gear purely in the direction of the gear axisapproaches mating tooth sides at different rates, at a slow rate on thelongitudinally convex tooth sides of the gear, at a fast rate on thelongitudinally concave side. More material is then pushed away on saidconcave side so that a substantial torque is exerted between die memberand gear. Also the forming action is very unequal on opposite sides.

One object of the invention is to reduce said torque and to improve theforming action. A further aim is to make the method applicable also tosuch cases where a cylindrical section coaxial with the gear shows anegative profile inclination on one side, so that this one side cannotbe reached with a purely axial approach. This condition occurs on somehypoid gears with large shaft offset.

Other objects are to provide novel apparatus and structures designed tocarry out the method of the invention in either forging or rollingoperations.

Another object is to avoid or decrease distortion in the production byrolling.

The foregoing and other objects and advantages of the invention willappear from the following description of the preferred embodimentsillustrated in the accompanying drawings, wherein:

FIG. I is a plan view of a bevel gear with some of its spirally arrangedteeth illustrated schematically thereon.

FIG. 2 is a side elevational view of the gear shown in FIG. 1.

FIG. 3 is an end elevational view of the gear shown in FIG. 1.

FIG. 4 is an enlarged and fragmentary sectional view taken along thecylindrical section line 15 of FIG. I and developed into a plane, andalso showing a tooth of the die member before full depth engagement andbeing fed axially into the gear.

FIG. 5 is a view corresponding to FIG. 4 and showing the tooth ofthe diemember being fed helically into the gear.

FIG. 6 is a view corresponding to FIG. 5 but showing gear teeth withnegative profile inclination on one side.

FIG. 7 is a partially sectioned and fragmentary view of a forging pressembodying the invention.

FIG. 8 is a diagrammatic view showing a gear in axial section at fulldepth engagement with a rotary die member, with the instant axis ofrelative motion in a preferred position adjacent the top of the dieteeth;

FIG. 9 is a view corresponding to FIG. 8 but showing the start of therolling operation.

FIG. 10 is a fragmentary and partially sectioned view of an apparatusembodying the invention and designed for the production of gears in arolling process.

FIG. 11 is a fragmentary plan view of a ring gear having spirallyarranged teeth that are curved lengthwise and which is designed to beproduced by the apparatus shown in FIG. 10.

Referring now to the drawings, FIG. 1 is a diagrammatic view ofa gear 8taken in the direction of its axis 9. Gear 8 has spirally arranged teeth10 which are shown as being curved lengthwise. They are indicated withtheir pitch lines only. Normal 11 in FIGS. 1, 2 and 3 is the toothsurface normal at mean point P of the tooth side facing outwardly. Thisis the side that is convex lengthwise. Normal 11 is inclined to a pitchplane 12 tangent to the pitch surface of gear 8 at an angle referred toas the pressure angle. It is inclined at a much smaller angle to a plane13 (FIG. 3) perpendicular to the gear axis 9. In FIG. 3 this angleappears as an angle 14. This is also the profile inclination of acylindrical section 15 (FIG. 1) coaxial with gear axis 9. It is theinclination to the axial direction of profile I6 of FIGS. 4 and 5. Theinclination of opposite profile I7 is much larger.

The inclination difference is further increased on hypoid gears. Whilespiral bevel gears have intersecting axes and about equal pressureangles on both sides of the teeth with respect to pitch plane 12, hypoidring gears generally have a lower pressure angle on the longitudinallyconvex side of the teeth than on the concave side. In some cases thismay result in a negative inclination of profile 16' of thelongitudinally convex tooth side, (FIG. 6).

The inclination difference of opposite tooth sides of spirally arrangedteeth is also apparent in the axial view of the gear 18 shown in FIG.11. The longitudinally convex tooth sides 20 are barely visible, whilethe concave tooth sides 21 appear wide.

The purely axial approach between die member 19 and gear 8, (FIG. 4),pushes away far more material adjacent side 17 than adjacent side I6.More pressure is exerted on side 17. This results in a substantialtorque load on both members and in unequal flow of material on oppositetooth sides. An inclined approach direction 9, in accordance with theinvention, improves the flow and reduces or even eliminates the torque.This direction is attained with a helical approach. The relativeapproach is along and about axis 9 of the work member 8.

FIG. 6 shows how such an approach extends the range of the process toinclude gears with negative inclination of profile 16', (FIG. 6).

Diagram FIG. 7 outlines a forging press operating with helical approach.Die member 19 is moved along and about its axis, that coincides withaxis 9 of the work member or prospective gear 8. Stationary hydrauliccylinder 25 extends about axis 9. Its piston 26 and ram 27 areconstrained to move in a helical path by a helical gear 28 rigidlysecured thereto and engaging a counterpart stationary internal helicalgear 30. Other forms of a helical constraint could be substituted ifdesired.

The die member 19 is secured to the front of gear 28. It contains aninternally tapered face surface and teeth that are the counterpart ofthe tooth spaces of the finished gear 8. A central portion 31 is securedto member 19, to form the inner ends of the gear teeth and the top 32 ofthe gear flange.

The outer tooth ends and the back of gear 8 are formed by a part 33coaxial with axis 9 and containing a hub 34. The bore or central openingis formed by a rod 35 placed inside of hub 34 and reaching into apreformed hole. Part 33 rests on base 36. Both part 33 and rod 35 aremaintained stationary during forging. For ejection of the gear, aftercompletion, part 33 is advanced axially, while rod 35 is keptstationary.

Strong ties 38 connect the base 36 with the upper end of cylinder 25.

It might be thought that a helical relative approach could also beattained without constraint by a turning motion of the work member whilethe die member has a purely axial approach, and that the work memberwould slide about its axis when the torque exerted thereon becomes toolarge. However the large axial pressure and high coefficient of frictionwould require a very large torque for such slippage.

A constrained helical approach according to the invention not only cankeep the torque low, but it securely holds the work member. This isparticularly important when forging is done with several strokes.

PRODUCTION BY ROLLING FIG. 8 shows a work member or gear 40 infull-depth engagement with a rotary die member or tool gear 41. Theiraxes 42, 43 intersect at apex 44. The die member may be a gear of largeface angle and sometimes a crown gear.

I preferably choose the tooth ratio and the angle between the axes 42,43 so that the instant axis 45 of relative motion extends along the faceof the die member or nearly so. Such determination can be attained withthe known procedures of the gear art. The instant axis 45 of relativemotion is close to the face surface of said die member and has a spacingfrom said face surface of between zero and one-fourth of its tooth depthall along the length of the teeth.

In other words the tooth ratio and angles are so selected that the facesurface of the die member rolls on the root surface of the gear atfull-depth position, FIG. 8. This gives rolling contact at the toothbottom where the maximum pressure is, and it minimizes sideswiping inthis critical region.

At the outset, before teeth are formed, the face of the smooth blankextends along dotted line 46 well inside of the final face profile 46.FIG. 9 shows the beginning of the rolling operation. While in knownpractice the relative approach is along axis 43 of the die member, ormore broadly in a direction approximately at right angles to the pitchsurface of gear 40, the invention uses an approach in the direction ofthe axis 42 of tapered gear 40. The instant axis 45 then remains fixedwith respect to the die member and keeps extending along its tooth tops.Thus the die member starts engagement at rolling motion withoutslippage. lt plunges straight into the blank.

FIG. 10 shows work member or gear 18 in the final position of engagementwith rotary die member 50. Work member 18 is secured to a cup part 51that is rotatably mounted on head 52 of plunger 53. It is journaledthereon by roller thrust bearing 54 and bearing 55. Plunger 53 ishydraulically operated to move in the direction ofthe gear axis 56.

Cup part 51 has helical spline 57 formed on its outside. They engagecounterpart helical splines provided inside of the hub 58 of a timinggear 60. Timing gear 60 is mounted on stationary portion 61 by bearings62, 63. It meshes with a timing gear 64 secured to the head 65 of thedie spindle with axis 66. The die member 50 is secured to head 65.

The flange containing timing gear 60 is provided with teeth 68 on itsoutside. Driving power is applied to them.

In operation the rotating work member 18 approaches the rotating diemember 50 in the direction of and angularly about its axis 56, asconstrained by the helical splines or guides 57. These are of the samehand as the hand of the spirally arranged teeth of gear 18, right handon the right-hand gear shown, left hand on a left-hand gear.

The process is not confined to rolling without previous indentation. Itmay also be used for finishing after teeth have already been formed.

What I claim is:

l. The method of producing tapered gears having spirally arranged teeth,which comprises relatively approaching a die member to a prospectivegear (a) in the direction of the axis of said gear and (b) alsoangularly about said axis to an end position where the resulting shapeis applied, the direction of said approach being the same as the hand ofthe spirally arranged teeth of said gear, and being right hand on aright-hand gear and left hand on a left-hand gear.

2. The method of producing tapered gears according to claim 1, wherein aforging die is relatively approached to a prospective gear in aconstrained helical motion about the axis of said gear.

3. The method of producing tapered gears according to claim 1, wherein atoothed die member and a prospective gear are rotated in timed relationon their respective axis while a relative approach is effected betweenthem in the direction of and angularly about the axis of said gear.

4. The method of producing tapered gears having spirally arranged teeth,which comprises rotating a toothed die member and a prospective gear onintersecting axes in timed relation so that the instant axis of relativemotion is close to the face surface of said die member and has adistance from said face surface between zero and one-fourth of its toothdepth all along the length of its teeth, and effecting relative approachbetween said die member and gear (a) in the direction of and (b)angularly about the axis of said gear to an end position where theentire resulting tooth shape is applied, the hand of said approach beingthe same as the hand of said ear 5. The method according to claim 4,wherein t e instant axis extends in the direction of the profile of theface surface of said die member in an axial section thereof.

6. The method according to claim 4, wherein the prospective gear ishelically approached about its axis to the die member.

7. In a forging machine, a die having an internally tapered annular facesurface and spirally arranged teeth following said face surface, saiddie being secured to a plunger movable along the axis of said facesurface, and positive means for constraining said plunger to turn aboutsaid axis as it moves along it.

8. In a rolling apparatus, a die member having spirally arranged teethdisposed along a circle, and a workpiece, means mounting said die memberand said workpiece for rotation about intersecting axes, and means foreffecting relative feeding motion between said die member and saidworkpiece simultaneously along and around the axis of said workpiece.

1. The method of producing tapered gears having spirally arranged teeth,which comprises relatively approaching a die member to a prospectivegear (a) in the direction of the axis of said gear and (b) alsoangularly about said axis to an end position where the resulting shapEis applied, the direction of said approach being the same as the hand ofthe spirally arranged teeth of said gear, and being right hand on aright-hand gear and left hand on a left-hand gear.
 2. The method ofproducing tapered gears according to claim 1, wherein a forging die isrelatively approached to a prospective gear in a constrained helicalmotion about the axis of said gear.
 3. The method of producing taperedgears according to claim 1, wherein a toothed die member and aprospective gear are rotated in timed relation on their respective axiswhile a relative approach is effected between them in the direction ofand angularly about the axis of said gear.
 4. The method of producingtapered gears having spirally arranged teeth, which comprises rotating atoothed die member and a prospective gear on intersecting axes in timedrelation so that the instant axis of relative motion is close to theface surface of said die member and has a distance from said facesurface between zero and one-fourth of its tooth depth all along thelength of its teeth, and effecting relative approach between said diemember and gear (a) in the direction of and (b) angularly about the axisof said gear to an end position where the entire resulting tooth shapeis applied, the hand of said approach being the same as the hand of saidgear.
 5. The method according to claim 4, wherein the instant axisextends in the direction of the profile of the face surface of said diemember in an axial section thereof.
 6. The method according to claim 4,wherein the prospective gear is helically approached about its axis tothe die member.
 7. In a forging machine, a die having an internallytapered annular face surface and spirally arranged teeth following saidface surface, said die being secured to a plunger movable along the axisof said face surface, and positive means for constraining said plungerto turn about said axis as it moves along it.
 8. In a rolling apparatus,a die member having spirally arranged teeth disposed along a circle, anda workpiece, means mounting said die member and said workpiece forrotation about intersecting axes, and means for effecting relativefeeding motion between said die member and said workpiece simultaneouslyalong and around the axis of said workpiece.